#pragma once
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <unordered_map>
#include <mutex>

#include "util.hpp"
#include "log.hpp"

namespace ns_index{
  
  struct DocInfo{
    std::string title;
    std::string content;
    std::string url;
    uint64_t doc_id; //文档ID
  };

  struct InvertedElem{//应用于倒排索引的结构
    uint64_t doc_id;  //文档ID
    std::string word; //关键词
    int weight;       //权重
  };

  //倒排拉链
  typedef std::vector<InvertedElem> InvertedList;

  class Index{
    private:
      //正排索引的数据结构用数组
      std::vector<DocInfo> forward_index;
      //倒排索引一定是一个关键字和一组（个）InvertedElem对应
      std::unordered_map<std::string, InvertedList> inverted_index;

    private:
      Index(){}
      Index(const Index&) = delete;
      Index& operator=(const Index&) = delete;

      static Index*instance;
      static std::mutex mtx;
    public:
      ~Index(){}
    public:
      static Index* GetInstance()
      {
        if(instance == nullptr){
          mtx.lock();
          if(instance == nullptr){
            instance = new Index();
          }
          mtx.unlock();
        }
        return instance;
      }


      //根据doc_id找到文档内容
      DocInfo *GetForwardIndex(uint64_t doc_id)
      {
        if(doc_id >= forward_index.size()){
          std::cerr << "doc_id out range. error!" << std::endl;
          return nullptr;
        }

        return &forward_index[doc_id];
      }

      //根据关键字string，获得倒排拉链
      InvertedList *GetInvertedList(const std::string &word)
      {
        auto iter = inverted_index.find(word);
        if(iter == inverted_index.end()){
          std::cerr << word << "have no InvertedList" << std::endl;
          return nullptr;
        }

        return &(iter->second);
      }
      
      //根据去标签，格式化后的文档，构建正排和倒排索引 
      bool BuildIndex(const std::string &input) //拿到parse处理完的数据
      {
        std::ifstream in(input, std::ios::in | std::ios::binary);
        if(!in.is_open()){
          std::cerr << "sorry, " << input << " open error" << std::endl;
          return false;
        }

        std::string line;
        int count = 0;
        //std::cout << "before build" << std::endl;
        while(std::getline(in, line)){
          DocInfo *doc = BuildForwardIndex(line);
          if(doc == nullptr){
            std::cerr << "build " << line << " error" << std::endl;
          }

          BuildInvertedIndex(*doc);
          count++;
          if(count % 50 == 0){
            std::cout << "当前已经建立的索引文档： " << count << std::endl;
            LOG(NORMAL, "当前的进度已经建立到" + std::to_string(count));
          }
        }
        
        return true;
      }
      private:
      DocInfo *BuildForwardIndex(const std::string &line)
      {
        //将传入的一个string按格式分割
        std::vector<std::string> results;
        const std::string sep = "\3";
        ns_util::StringUtil::Split(line, &results, sep);
        if(results.size() != 3){
          return nullptr;
        }
        //用分割结果填充一个DocInfo结构
        DocInfo doc;
        doc.title = results[0];
        doc.content = results[1];
        doc.url = results[2];
        doc.doc_id = forward_index.size();
        //将填充好的DocInfo插入到正排索引
        forward_index.push_back(doc);
        return &forward_index.back();
      }

      bool BuildInvertedIndex(const DocInfo &doc)
      {
        struct word_cnt{
          int title_cnt;
          int content_cnt;

          word_cnt():title_cnt(0), content_cnt(0){}
        };
        std::unordered_map<std::string, word_cnt> word_map;

        //对标题
        std::vector<std::string> title_words;
        ns_util::JiebaUtil::CutString(doc.title, &title_words);

        for(std::string s: title_words){
          //统一字母大小写
          boost::to_lower(s);
          word_map[s].title_cnt++;
        }

        //对文本
        std::vector<std::string> content_words;
        ns_util::JiebaUtil::CutString(doc.content, &content_words);

        for(std::string s: content_words){
          boost::to_lower(s);
          word_map[s].content_cnt++;
        }

        //构建倒排索引
#define X 10
#define Y 1
        for(auto &word_pair : word_map){
          InvertedElem item;
          item.doc_id = doc.doc_id;
          item.word = word_pair.first;
          item.weight = X*word_pair.second.title_cnt + Y*word_pair.second.content_cnt; //相关性
          
          InvertedList &inverted_list = inverted_index[word_pair.first];
          inverted_list.push_back(std::move(item));
        }


        return true;
      }

  };

  Index* Index::instance = nullptr;
  std::mutex Index::mtx;
}




















































